This invention relates generally to bone resection apparatus for use in the implantation of artificial joints, such as a total knee prothesis or the like. More particularly, this invention relates to an improved tibial cutting jig for accurate resection of the tibia to insure optimum placement of the tibial component of a total knee prothesis.
Prosthetic joint devices such as total knee protheses are relatively well known in the art for implantation into the body. Such knee protheses typically include a femoral and a tibial component designed for respective affixation to the femur and tibia and further including mating bearing surfaces designed to accommodate articulated knee motion. Component affixation to patient bone has normally required at least some resection and shaping of femoral and tibial surfaces at the knee joint, with the components thereafter being secured to the bone by a press-fit attachment, by use of a selected bone cement, by use of porous bone ingrowth surfaces, or by a combination of these techniques. Exemplary total knee protheses are described in more detail in U.S. Pat. Nos. 4,355,429 and 4,085,466.
In total knee protheses, the complex geometry of the knee joint together with the complex mechanical loading thereof during normal function makes it extremely important for the prosthetic components to be accurately aligned and securely seated on the patient bone. More particularly, the tibial component comprises the primary load bearing component and must be positioned properly on the proximal or upper end of the tibial with minimal shear forces at the prothesis-bone interface. Otherwise, during normal knee function, these shear forces can cause the tibial component to become dislodged resulting in failure of the prothesis, wherein such failure can be repaired, if at all, only by additional surgery.
In the past, various operative procedures have been followed for preparing the tibial proximal end for mounting of the tibial component of a total knee prothesis, wherein such procedures have predominantly envisioned resection of the tibial plateau on a plane generally perpendicular to the tibial longitudinal axis. In accordance with one common technique, this resection has been performed with a power saw along a free hand cut without the use of any saw guide or other measurement/alignment apparatus. However, this approach clearly requires a high degree of surgeon skill to avoid inaccurate resection and frequently requires multiple cuts on a trial and error basis to achieve accurate alignment and seating of the tibial component. Other bone cutting techniques have utilized saw guides mounted on intramedullary femoral alignment rods preinstalled along the femoral longitudinal axis. However, such saw guides have not been applied for use with the tibia and in any event have been adjustably positioned according to measurements referenced from the intramedullary rod. Accordingly, any inaccuracy in placement or settling of the intramedullary rod has resulted in a correspondingly inaccurate resection, thereby frequently requiring a trial and error fitting of the tibial component.
There exists, therefore, a significant need for an improved device for obtaining a precision resection of the tibial plateau in the course of a total knee prosthesis implantation procedure. The present invention fulfills this need and provides further related advantages.